1. Field of the Invention
This invention relates to an endoscope for examination of internal faces of body cavities, and more particularly to an endoscope having a cleaning device for cleaning the viewing window of the endoscope after insertion into a body cavity. The endoscope in accordance with the present invention is of the type in which a demountable hood is provided at the end thereof.
2. Description of the Prior Art
It has been known in the art to provide a cleaning device on an endoscope which is inserted into body cavities for examination of the internal faces thereof. The endoscope is usually comprised of an objective lens system, an image transmitting fiber optical tube, an eyepiece lens system and an illumination system to illuminate the internal faces of the body cavities into which the endoscope is inserted. The cleaning device is usually comprised of an injection nozzle provided near the viewing window at the end of the endoscope, an air and water transfer conduit extending through the endoscope along the image transmitting tube and a suction pipe extending through the endoscope along said tube and having an open end at the end of the endoscope. Cleaning water and/or air is supplied on the viewing window of the endoscope in the body cavity to clean the surface of the viewing window glass and is taken out of the body cavity through the suction pipe. The suction pipe usually has a single open end at the front end of the endoscope since the structure of the endoscope does not allow the suction pipe to have more than one opening at the end of the endoscope.
The above described endoscope with a cleaning device has a defect in that the drainage cannot be conducted efficiently when the open end of the suction pipe is positioned at a higher level than the injection nozzle. Therefore, when using the cleaning device of the endoscope, the operator must be careful to keep the open end of the suction pipe at a lower level than the injection nozzle.
It has also been known in the art to mount a hood at the end of an endoscope to keep the viewing window glass off the internal faces of the body cavity. The endoscope with the cleaning device and the hood is disadvantageous in that the cleaning water and liquid in the body cavity are likely to stay within the hood and hinder the observation of the internal faces through the viewing window.